Structure and method for compaction of powder-like materials

ABSTRACT

Structure and a method for producing very dense bodies from particulate materials. An electrically conductive drive member is positioned adjacent the particulate material. A significant magnitude of electrical current is caused to flow through the electrically conductive drive member. A magnetic field is established and large magnitudes of magnetic pressure are created, and pressure directly from or indirectly from the magnetic pressure is applied upon the particulate material, and the particulate material is compressed and compacted. In one embodiment of the invention electrical current creates a magnetic field which is applied to an electrically conductive pressure member which moves and applies compaction pressure upon the particulate material. Electromagnetic pressure in accordance with this invention may be applied to a compacted body of particulate material, and the compressibility and density of the body of particulate material is increased. Any one of numerous types of particulate material may be involved with regard to this invention.

RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.07/834,148, filed Feb. 10, 1992, now U.S. Pat. No. 5,405,574.

BACKGROUND OF THE INVENTION

Several methods have been employed for forming particulate orpowder-like materials into a unitary firmly compacted body of material.

Powdered metal bodies have been formed by means of pressure and heat.Such a method has also been used for forming unitary bodies from otherpowder or particulate materials.

A problem has specifically existed with regard to formingsuperconducting powders into a unitary firmly compacted body. Ceramicsuperconducting powders are normally prepared by proportioning thespecific quantities of selected oxides. The combination is thenthoroughly mixed by conventional means and then fired at elevatedtemperatures in suitable gaseous atmospheres. The induced solid statereaction causes the formation of the desired ceramic compositions andlattice structures.

In ceramic superconductors, the superconductivity within individualcrystallites is proximity coupled to neighboring grains. Consequently,the orientation and coupling between crystallites are key factorsaffecting the current carrying capacity of the bulk ceramicsuperconductors. Voids, cracks, and grain boundaries act as weak linksbetween crystallites and reduce the critical currents within the bulkmaterial. Therefore, a technique which produces dense ceramics with goodintergrain coupling and by which the material is formable into desiredshapes to yield a required superconducting characteristic is ofsignificant value.

At the present time several methods are used for obtaining high criticalcurrent densities in bulk superconducting materials.

One method employed is that of melt textured growth of polycrystallingmaterial. This method is discussed in a paper included in Volume 37, No.13, May 1, 1988, Physical Review B, S. Gin, et al, entitled:Melt-Textured Growth of Polycrystaline. This method consists of heatinga bulk specimen of the high temperature material in a furnace totemperatures at which partial melting occurs. A temperature gradient ismaintained in the furnace, and the superconductor is melted andrecrystallised as the specimen is passed through the hot zone. Highlytextured material is produced through this method and at present isshown to yield high Jc values. This method is generally limited to theprocessing of small length samples.

Another method is that of placing powder in a tube. This "powder intube" method is discussed in a paper 1989 Applied Physics Letters, page2441 , prepared by K. Heine, et al, entitled: High-Field CriticalCurrent Densities. In the "powder in tube" method, mechanicaldeformation is used to align plate-like particles of bismuth basedsuperconductors. The powder is loaded into a tube of silver material andthe assembly is compacted by swaging, drawing or rolling. A silversheath provides a path to shunt currents across any defects. Thematerial is subsequently heat treated to obtain the optimumsuperconductor characteristics.

However, as a result of the nature of varied mechanical operationinvolved in the two methods discussed above, reproducing the manyprocessing steps repeatedly during fabrication of long lengths of wiresand tapes remains unsatisfactory.

Another method of compaction is that of hot extrusion. This method isdiscussed in an article entitled: Hot Extrusion of High-temperatureSuperconducting Oxides by Uthamalingam Balachandran, et el, AmericanCeramic Bulletin, May 1991 , page 813.

Another method is discussed in U.S. Pat. No. 5,004,722, Method of MakingSuperconductor wires By Hot Isostatic Pressing After Bending.

Another compaction technique which has been employed pertains to a shockmethod. This method is discussed in an article entitled:Crystallographically oriented superconducting Bi₂ Sr₂ CaCu₂ O₈ by shockcompaction of prealigned powder by C. L. Seaman, et al, in AppliedPhysics Letters 57, dated Jul. 2, 1990 , page 93.

Another method of compaction is that known as an explosive method,discussed in an article entitled: Metal Matrix High-TemperatureSuperconductor, by L. E. Murr, et al, in Advanced Materials andProcesses Inc. Metal Progress, October 1987, page 37.

These methods are limited in value because they are generally applicableonly to production of small body sizes.

The application of large uniaxial static pressures at elevatedtemperatures is discussed in an article entitled: Densification of YBa₂Cu₂ O₇₋₈ by uniaxial pressure sintering, by S. L. Town, et al, inCryogenics, May 1990, Volume 30.

The use of electromagnetic forming for the purpose of attachment isdiscussed in a paper entitled: Electromagnetic Forming, by J. Bennettand M. Plum, published in Pulsed Power Lecture Series, Lecture No. 36.

However, processing of long lengths of homogenous and high qualitysuperconducting tapes or wires by the processes discussed above has notbeen realized.

It is an object of this invention to provide a method and means forproducing high density bodies by the use of powder-like and/orparticulate materials.

It is another object of this invention to provide a method and means forproducing electrical conductors by the use of powder-like or particulatematerials.

It is another object of this invention to provide a method and means forproducing high quality and continuous superconducting electricalconductors such as wires and tapes.

It is another object of this invention to provide such a method whichcan be consistently precisely duplicated in the quality of production.

Other objects and advantages of this invention reside in the structuresand the construction of parts, the combination thereof, and the methodsemployed, as will become more apparent from the following description.

SUMMARY OF THE INVENTION

In this invention, powder-like and/or particulate materials or the likeare compacted into high density bodies. The high density bodies can beof various shapes and sizes, and may, for example, be bodies such asrods, tapes, tubes, or plates or wheels or any other suitably shaped ordesirably shaped bodies.

One method and related structure of this invention applies pressuresgenerated by non-contact electromagnetic forces. These electromagneticpressures are generated by employing suitably shaped coils, such assolenoids or the like which have the necessary current carryingcapacity. In this process a suitable electrically conductive containeris encompassed by such a coil or solenoid. Within the electricallyconductive container powder-like material is enclosed. When highmagnitudes of electrical current are passed through the solenoid orcoil, very high pressures are applied to the electrically conductivecontainer, and the electrically conductive container is reduced intransverse dimensions. Thus, the powder-like material within theelectrically conductive container is compacted into a body of highdensity.

With regard to this invention, compaction of particulate material ispreferably performed by electromagnetic compaction as electrical energyis applied in short time pulses.

In one embodiment of this invention particulate material is compressedby means of a magnetizable wall or other type of pressure member whichis moved by electromagnetic forces.

Pressures which are applied by the methods and/or structures of thisinvention may be applied to particulate material upon which no priorcompaction pressure has been applied. Pressures which are applied by themethods and/or structures of this invention may be applied to a body ofparticulate material which has earlier received compaction pressure bymechanical means or by other types of pressure application. If a body ofparticulate material has been compacted by mechanical means or by anyother means, additional application of compaction pressure in accordancewith a method and/or structure of this invention may be referred to as arestrike application of compaction pressure.

Numerous types of rigid bodies are comprised of particulate material inwhich the particulate material is compressed by mechanical means. Eachparticle in a body of particulate material has a thermal time constantwhich is related to the size of the particle of a given material, andwhich is also related to the thermal conductivity of the particle andwhich is also related to the heat capacity of the particle, and which isalso related to the density of the particle. Thus, the relationship isas follows: ##EQU1## in which T represents the thermal time constant ofthe particle, D represents the density of the particle, C represents theheat capacity of the particle, K represents the thermal conductivity ofthe particle, and R represents the size of the particle. Each of thesefactors is related to the material of which the particle is comprised.

In regard to this invention, it has been found that if electricalmagnetic compaction of a given magnitude of pressure occurs in a timeperiod which is less than the thermal time constant of a particle uponwhich pressure is applied, then the particle will have greatercompressibility, that is, the particle will have greater compressibilitythan the compressibility which occurs when mechanical pressure of thesame magnitude is applied. The relationship in regard to this statementis as follows: When the pulse time of applied magnetic pressure is lessthan the thermal time constant of the particle greater compressibilityof the compressed particle is obtained.

Example for particulate steel:

D=7870 kg/m³

C=473 J/kg °K.

K=40 w/m °K.

So for R=50×10⁻⁶ m

T is less than 233×10⁻⁶ seconds

In which T represents the pulse time of applied magnetic pressure; Jrepresents joules; kg represents kilograms; °K. represents degreesKelvin; w represents watts; m represents meters.

Furthermore, in regard to this invention, it has been found that thedensity of a body which comprises particulate material can be increasedby a predetermined number of applications of electromagnetic pulses ofshort time duration, each of the pulses having a pulse time which isless than the thermal time constant of the particle. Therefore, nointermediate sintering or heat treating is required. For example: forcompaction of a body of an alloy powder of steel, three (3) pulsesprovide optimum or maximum density in the body. For compaction of a bodyof particulate copper, two (2) pulses create optimum or maximum densityin the body. For compaction of bodies of other materials in particulateform, the number of pulses to obtain maximum density may be more than orfewer than two or three.

In one embodiment of this invention particulate material is placed uponan electrically conductive strip, and the strip is formed into a tubularmember, thus enclosing the particulate material. The tubular member isencompassed by a solenoid or coil. High current levels are passedthrough the solenoid or coil, and a high magnitude of resultingelectromagnetic pressure is applied to the tubular member. Thetransverse dimensions of the tubular member are significantly reducedand the particulate material within the tubular member is thus firmlycompacted. If desired, this process can be performed in a continuousmanner, so that an elongate conductor of compacted material is produced.This compaction method of this invention is capable of producing wire ortape or the like.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS

FIG. 1 is a perspective diagrammatic view illustrating a structure and amethod of compaction of powder-like materials in accordance with thisinvention.

FIG. 2 is a perspective diagrammatic type of view illustrating a methodand structure in accordance with this invention for producing in acontinuous process an elongate member, which may be referred to as awire, or tape, or the like. The process illustrated can be employed forproduction of an elongate member of material.

FIG. 3 is a fragmentary perspective sectional diagrammatic viewillustrating another embodiment of structure for compaction ofparticulate material in accordance with this invention.

FIG. 4 is a fragmentary perspective sectional diagrammatic view, similarto FIG. 3, showing the structure as it contains particulate materialprior to compaction of the particulate material.

FIG. 5 is a fragmentary perspective sectional diagrammatic view, similarto FIGS. 3 and 4, illustrating the structure and particulate materialafter compaction of the particulate material.

FIG. 6 is a perspective view illustrating a wheel-like body which hasbeen produced by the structure of FIG. 3.

FIG. 7 is a sectional diagrammatic view illustrating another embodimentof the structure of this invention. This view also shows particulatematerial within a portion of the structure.

FIG. 8 is a sectional diagrammatic view, similar to FIG. 7, showing thestructure of FIG. 7 and showing the particulate material aftercompaction thereof.

FIG. 9 is a sectional diagrammatic view illustrating another embodimentof the structure of this invention. This view shows particulate materialwithin the structure prior to compaction of the particulate material.

FIG. 10 is a sectional diagrammatic view, similar to FIG. 9, showing thestructure and the particulate material after compaction of theparticulate material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a direct current power supply 20 to which is connectedelectric conductors 22 and 24. Connected to the conductor 22 is a switch26 which is also connected to a conductor 28. The conductor 28 and theconductor 24 have joined therebetween a capacitor 30. The conductor 28is also connected to a switch 32 which is also connected to a conductor34. The conductor 24 and the conductor 34 are connected to a solenoid orcoil 36 which encompasses an electrically conductive container 38. Theelectrically conductive container 38 is shown as being rectangular intransverse dimensions. However, the electrically conductive container 38may be of any suitable or desired shape and size. The electricallyconductive container 38 may be of any suitable electrically conductivematerial, such as, for example, of silver material.

Within the electrically conductive container 38 is a quantity of powdermaterial 40. The powder material 40 completely fills the electricallyconductive container 38 and is firmly positioned therewithin.

In carrying out the process of this invention, the switch 26 is closed,and the capacitor 30 is charged from the power supply 20. After thecapacitor 30 is completely charged, the switch 26 is opened and theswitch 32 is closed. When the switch 32 is closed a large quantity ofelectrical current flows from the capacitor 30 through the solenoid orcoil 36. When electrical current flows through the coil or solenoid 36magnetic pressure is applied upon the electrically conductive container38. This pressure acts inwardly upon the electrically conductivecontainer 38, and the transverse dimensions of the electricallyconductive container 38 are reduced. Thus, compression occurs within theelectrically conductive container 38, and the powder-like material 40within the electrically conductive container 38 is compressed andcompacted. Thus, the powderous material 40 within the electricallyconductive container 38 becomes a dense body.

As an example or illustration, the electrically conductive container 38may have a transverse dimension of less than one inch or several inches,and current flow through the solenoid 36 may be in the order of about100,000 amperes at a voltage of about 4,000 volts. It is to beunderstood, of course, that other magnitudes of current may be employedas found to be suitable in accordance with the size and physicalcharacteristics of the electrically conductive container 38 and thephysical characteristics and volume of the powder-like material 40. Itis also to be understood that when the powder-like material 40 has goodelectrically conductive properties, a container may not be necessary orthe container of the particulate material may not need to beelectrically conductive for compaction of the particulate material inaccordance with the method and/or structure of this invention.

Due to the fact that the solenoid or coil 36 tends to expand radially ascurrent flows therethrough, suitable means are employed to restrain thecoil 36 against lateral expansion as current flows therethrough. Forexample, as shown, a rigid wall 44 closely encompasses the coil 36 andrestrains the coil 36 against expansion as current flows therethrough.

FIG. 2 illustrates structure and a method of the construction of anelongate body, such as a wire or tape or rod in accordance with thisinvention. A strip of electrically conductive material 50 in a flatcondition is moved longitudinally as illustrated by arrows 52. Apowderous material 54 having desired physical or electrical propertiesis poured upon the strip 50. When a superconductive body is desired, thepowderous material 54 is superconductive material. Thus, the strip 50carries the powder-like material 54.

Then by any suitable means, such as by means of a forming unit 55, thestrip 50 is formed into a tubular member 50a, as the tubular member 50aencloses and carries the powder-like material 54. Then the diameter ofthe tubular member 50a is reduced as the tubular member 50a is drawnthrough a drawing unit 57. Thus, the diameter of the tubular member 50ais reduced as elongation of the tubular member 50a occurs. Thus, adegree of compaction of the powder-like material occurs as drawing andelongation of the tubular member 50a occurs.

Then the tubular member 50a is moved into the confines of a solenoid ora coil 56. The coil 56 is energized from a power source 60. Electricalconductors 62 and 64 are connected to the power source 60. Joined to theconductor 64 is a switch 66. A conductor 67 is also connected to theswitch 66. Connected to the conductors 62 and 67 is a capacitor 68. Alsoconnected to the conductor 67 is a switch 72. Also connected to theswitch 72 is a conductor 74. The conductor 74 and the conductor 62 arejoined to the solenoid or coil 56.

In accordance with the method of this invention, the capacitor 68 ischarged from the power source 60 as the switch 66 is closed. Then theswitch 66 is opened, and the switch 72 is closed so that a largemagnitude of current flows from the capacitor 68 through the coil orsolenoid 56, as illustrated by arrows 76. The flow of current throughthe coil 56 may be in the order of several thousand amperes. When thisflow of current through the solenoid or coil 56 occurs a high magnitudeof magnetic pressure is applied to the tubular member 50a. The pressureupon the tubular member 50a causes reduction of the transverse dimensionof the tubular member 50a. Thus, the powder material 54 within thetubular member 50a becomes very firmly compacted. Due to the fact thatthe coil 56 tends to expand during current flow therethrough, a wall 80closely encompasses the coil 56 and restrains the coil 56 against radialand axial expansion.

If desired, after the tubular member 50a passes through the electricalcoil 56, the tubular member 50a, with the powderous material 54compacted therewithin, may pass through a sintering operation 84. Thesintering operation 84 improves the properties of the compactedpowder-like material 54. Power driven roller means 85 are shown formoving the tubular member 50a.

By this means and method, a desired elongate body can be produced. Bythis means and method a superconducting wire or tape or the like can beproduced. As illustrated, the process can be a continuous process. Bycontinuously moving the tubular member 50a through the solenoid 56 whilecurrent flows through the 56, continuous lengths of tubes are compacted,and a continuous length of electrical conductor of superconductingmaterial is produced. Thus, superconductors of any desired shape andsize and/or length can be produced in a single operation or in acontinuous operation or in plurality of operations. Long lengths ofsuperconducting material can be repeatedly and precisely produced bythis non-contact method. After processing, the wire of superconductingmaterial may be wound into a coil 86, as shown in FIG. 2.

The method and structure shown in FIG. 2 have been found to besuccessful in creating a wire-like conductor of superconductingmaterial. As an example or illustration, a wire of superconductingmaterial was produced in which the strip 50 was approximately one-halfinch in width and approximately fifteen thousandths of an inch inthickness. The superconductive powder material 54 employed wasBi(Pb)SrCaCuO. The current flow through the coil 56 was in the order ofabout one hundred thousand amperes. After travel through the coil 56 thetransverse dimension of the tubular member 50a was about one-eighth ofan inch.

It is to be understood that the method of this invention can be employedin compacting most types of powder-like or powderous materials, such asceramic compounds, ceramic and metal composites, metals, metal alloys,and metal compounds.

FIGS. 3, 4, and 5 illustrate another embodiment of structure of thisinvention for compaction of particulate material. These figures show anelectrical coil 90 which encompasses a solid support member 92. Theelectrical coil 90 has connection portions 94 and 96, for connection toa suitable power supply, not shown. A housing 100 encloses theelectrical coil 90 and the support member 92. The housing 100 has anannular inner toothed region 101. FIG. 4 shows particulate material 102within the housing 100. A portion of the particulate material 102engages the toothed region 101. A wall member 104 separates theparticulate material 102 from the electrical coil 90. The wall member104 comprises electrically conductive material, such as aluminum or thelike. The wall member 104 is expandable in length or circumference.

When the electrical coil 90 is energized by a suitable magnitude ofelectrical current, a magnetic field is created and magnetic pressure isapplied to the electrically conductive wall member 104. When magneticpressure is applied to the wall member 104, the wall member 104 movestoward the particulate material 102. The wall member 104 expands incircumference and pressure is applied to the particulate material 102,within the housing 100.

Therefore, as illustrated by FIG. 5, the particulate material 102 iscompressed and a highly dense body of particulate material is formed.Therefore, as illustrated in FIG. 6, an annular toothed wheel 102A orthe like is formed by the structure and method of this invention.

After production of the toothed wheel 102A, the wall member 104 may beremoved from the toothed wheel 102A or left upon the toothed wheel 102Ato be used as a part of the toothed wheel 102A.

If the particulate material 102 includes electrically conductivematerial, the wall member 104 may not need to be electricallyconductive, and it may not be necessary to move the wall member 104toward the particulate material 102 for compaction of the particulatematerial 102 by means of magnetic pressure applied by energization ofthe electrical coil 90.

FIGS. 7 and 8 illustrate another embodiment of the structure of thisinvention. The structure of FIGS. 7 and 8 comprises a first housingmember 112 and a second housing member 116. The first housing member 112has a recess 118, within which an electrically conductive stem 120 ismovably positioned. Encompassing the stem 120 is an electricallyconductive coil 124, which has connection portions 128 and 130. A packermember 134 is attached to the stem 120. The second housing portion 116has a chamber 140 which is adapted to retain particulate material 144,as shown in FIG. 7.

When the electrically conductive coil 124 is energized a magnetic fieldis created and magnetic forces upon the stem 120 and the packer member134 force the packer member 134 into the chamber 140, and pressure isapplied to the particulate material 144. The pressure applied to theparticulate material 144 compacts the particulate material 144, and arigid body 44A is formed, as shown in FIG. 8.

FIGS. 9 and 10 illustrate another embodiment of the structure of thisinvention. An outer housing 150 encloses an inner housing 154. The outerhousing 150 is shown as engaging a base 158. A plate 160 divides thebase 158 from one end part of the inner housing 154. At the other end ofthe inner housing 154 a plate 166 separates the inner housing 154 frominsulator members 170 and 172. The outer housing 150 and the innerhousing 154 and the base 158 and the plate 66 are constructed ofelectrically conductive material.

In engagement with the plate 166 and extending therefrom is anelectrically conductive member 180. The electrically conductive member180 extends through the insulator member 172. A wire-like electricconductor 188 joins the electrically conductive member 180 to a powersupply unit 194. A wire-like electric conductor 198 joins the powersupply unit 194 to wire-like electric conductor member 200. The electricconductor member 200 is shown as having two portions, each of which isconnected to the outer housing 150. Electric current is shown by arrows210 as traveling from the power supply unit 194, through the electricconductor 200 to the outer housing 150. Electric current flows throughthe outer housing 150, through the base 158, and through the plate 160.The electric current then flows from the plate 160 through the innerhousing 154 and through the plate 166, and through the electricallyconductive member 180, to the wire-like electric conductor 188, and intothe power supply unit 194. Thus, an electric current circuit isestablished, and current flows substantially as indicated by the arrows210.

The inner housing 154 is adapted to contain particulate material 220.FIG. 9 shows the particulate material 220 prior to compaction thereof.When electrical current flows in the manner illustrated by the arrows210, electromagnetic pressure is created upon the inner housing 154. Theinner housing 154 is formed by wall members which are of flexiblematerial, such as aluminum or the like. Thus, when magnetic pressure isapplied upon the inner housing 154, the transverse dimension andcircumference of the inner housing 154 is decreased, as illustrated inFIG. 10. Thus, the particulate material 220 within the inner housing 154is compressed, as illustrated in FIG. 10. As the diameter andcircumference of the inner housing decreases, there is sliding actionbetween the inner housing 154 and the plate 160 and the plate 166. Thus,a body of dense particulate material 220 is formed, as shown in FIG. 10.

Therefore, it is understood that the structure and method of thisinvention are effective in compaction of particulate materials.Particulate material can be compacted by non-contact electricallyconductive means, or compaction pressure can be applied to particulatematerial by means of an electrically conductive pressure member which ismoved by magnetic forces upon the pressure member.

Also, it is to be understood that the structure and method of thisinvention are capable of providing greater compressibility and greaterdensity to a body of particulate material than is possible by mechanicalmeans of the same magnitude of pressure.

It is also to be understood that the structure and method of thisinvention may be applied for production of bodies of particulatematerial of any one of various sizes and shapes and any one of variousmaterials.

Although the preferred embodiment of the structure and method forcompaction of particulate materials of this invention has beendescribed, it will be understood that within the purview of thisinvention various changes may be made in the structure and/or method, orin the form, details, proportion and arrangement of parts, or thecombination thereof, which generally stated consist in a structure andmethod within the scope of the appended claims.

The invention having thus been described, the following is claimed:
 1. Astructure for producing a dense body using a powder material,comprising:a retainer for retaining the powder material, an electricallyconductive pressure member movable toward the powder material which isretained by the retainer, an electrically conductive driver positionedadjacent the electrically conductive pressure member, an electricalenergy supply source to energize the electrically conductive driver forenergization of the electrically conductive driver to applyelectromagnetic pressure to the electrically conductive pressure memberwithout direct electrical contact to drive the electrically conductivepressure member to compress the particulate material to produce saiddense body.
 2. A structure for increasing the density of a powder,comprising:a support for receiving and supporting the powder, anelectrically conductive driver positioned adjacent the support, aconnector for connecting the driver to a source of electrical energy forenergization of the driver to create a magnetic field for applyingpressure to the powder without direct electrical contact therebetween toincrease the density thereof, thereby producing an integeral part fromsaid powder.
 3. The structure of claim 2 in which the electricallyconductive driver and the powder are in adjacent relationship so thatone of them is positioned in adjacent relationship to the other.
 4. Thestructure of claim 2 which includes an electrically conductive wallmember positioned between the powder and the electrically conductivedriver, the electrically conductive wall member including a movableportion, whereby energization of the electrically conductive drivercreates a magnetic field within the electrically conductive wall memberand applied electromagnetic pressure to the electrically conductive wallmember and a movable portion of the electrically conductive wall memberis moved toward the powder and pressure is applied to the powder forincreasing the density of the powder to form a densified body.
 5. Thestructure of claim 2 which comprises an electrically conductive wallmember which is positioned between the powder and the electricallyconductive driver and in which the electrically conductive wall memberencompasses the powder.
 6. The structure of claim 2 which comprises anelectrically conductive wall member which is positioned between thepowder and the electrically conductive driver and in which the powderencompasses the electrically conductive wall member.
 7. A structure forproducing a dense body of particulate material, comprising:a containerprovided with an annular recess for retaining particulate material, thecontainer also being provided with an inner chamber, the annular recessencompassing the inner chamber, an electrical conductor driverpositioned within the inner chamber and energizable to create a magneticfield and to apply electromagnetic pressure toward the annular recessfor applying pressure upon particulate material which is within theannular recess, whereby the particulate material within the recess iscompressed to provide a dense body without direct electrical contactbetween said driver and said material.
 8. The structure of claim 7 whichincludes an electrically conductive pressure member positioned betweenthe inner chamber and the annular recess, the electrically conductivepressure member being movable by the magnetic field toward the annularrecess for applying pressure upon particulate material which is withinthe annular recess.
 9. The structure of claim 7 which includes anannular electrically conductive wall member positioned between the innerchamber and the annular recess, the annular electrically conductive wallmember having movable portions, the annular electrically conductive wallmember being energized by the magnetic field with energization of theelectrical conductor driver, whereby movable portions of the annularelectrically conductive wall member are movable toward the annularrecess for applying pressure upon particulate material which is withinthe annular recess for providing an annular body of compactedparticulate material.
 10. A magnetic compactor device for producing awheel which is comprised of compressed particulate material, comprisinga container, the container being provided with an annular recess, theannular recess being adapted to retain particulate material, anelectrical conductor adjacent the annular recess, a cylindricalelectrically conductive wall member positioned between the annularrecess and the electrical conductor, the electrical conductor beingenergizable to create a magnetic field and to apply magnetic pressureupon the cylindrical electrically conductive wall member to move thecylindrical electrically conductive wall member toward the recess tocompress the particulate material to produce said wheel without directelectrical contact between the electrical conductor and the wall member.11. A structure for producing a dense body of particulate material,comprising a housing, an electrically conductive stem having a portionwithin the housing, the electrically conductive stem being movable withrespect to the housing, an electrical conductor encompassing the stem,the electrical conductor being energizable to create a magnetic fieldand to apply electromagnetic force to the electrically conductive stemfor movement of the electrically conductive stem with respect to thehousing, a retainer adjacent the housing for retaining said particulatematerial, whereby energization of the electrical conductor creates amagnetic field which moves the electrically conductive stem and theengagement means toward the retainer and toward the particulate materialwithin the retainer and compaction pressure is applied to theparticulate material and the particulate material is compressed and adense body of particulate material is produced without direct electricalcontact between the electrical conductor and the retainer.
 12. Astructure for producing a body of compacted particulate materialcomprising a cylinder for receiving electrically conductive material,said cylinder having movable wall portions, for receiving electricallyconductive material, means for applying magnetizing energy to thecylinder to create a magnetic field which is applied to the cylinder forslidably moving the movable wall portions of the cylinder to applypressure upon particulate material within the cylinder for compactingthe particulate material to provide an internal body of compactedparticulate material without direct electrical contact between saiddriver and said cylinder.
 13. A structure for producing a body ofcompacted particulate material comprising cylinder means, the cylindermeans having movable wall portions, stationary plates at the respectiveends of said removable wall portions, slidable engagement means slidablyengaging the movable wall portions of the cylinder, the cylinder meansbeing adapted to contain particulate material, the cylinder meansincluding electrically conductive material, a driver for applyingmagnetizing energy to the cylinder means to create a magnetic fieldwhich is applied to the cylinder means for slidably moving the movablewall portions of the cylinder means to apply pressure upon particulatematerial which is within the cylinder means for compacting theparticulate material and providing a body of compacted particulatematerial in which the cylinder means comprises an inner cylinder and anouter cylinder, the inner cylinder having movable wall portionscontaining the particulate material and being slidably movable upon theslidable engagement means, the outer cylinder and the inner cylinderbeing of electrically conductive material, means for conducting flow ofelectrical current within the outer cylinder, whereby electrical currentflowing in the outer cylinder creates a magnetic field which is appliedto the inner cylinder for slidably moving the movable wall portions ofthe inner cylinder along said stationary plates to apply pressure uponthe particulate material within the inner cylinder for compacting theparticulate material within the inner cylinder and providing a body ofcompacted particulate material.
 14. Structure for producing a body ofcompacted particulate material, comprising a first wall member and asecond wall member, the first wall member and the second wall memberbeing in adjacent relationship, the first wall member having anelectrically conductive movable portion adapted to contain particulatematerial,electrically conductive slide engagement means slidablyengaging the electrically conductive movable portion of the first wallmember, the electrically conductive movable portion of the first wallmember having a first position and a second position, the second wallmember being of electrically conductive material, means for establishingflow of electrical current through the second wall member for creatingan electromagnetic field within the first wall member for moving theelectrically conductive movable portion of the first wall member fromthe first position thereof to the second position thereof forcompressing and compacting the particulate material which is containedby the electrically conductive movable portion of the first wall memberand producing a body of compacted particulate material.